Vitamin D Deficiency: Symptoms, Causes and Treatment

You spend most of the week indoors, your legs feel heavier on the stairs and an online symptom list seems to explain everything. Vitamin D deficiency is one possibility, but it is not the only one. Many people with low vitamin D have no obvious symptoms, while tiredness and body aches can come from sleep problems, iron deficiency, thyroid disorders and several other conditions. The useful next step is to look at your risk factors and decide with a healthcare professional whether testing is needed.

What is vitamin D and why is it important?

Vitamin D is a fat-soluble vitamin that the body can make when skin is exposed to ultraviolet B light. It can also come from food and supplements. The National Institutes of Health Office of Dietary Supplements explains that vitamin D helps the body absorb calcium and supports normal bone, muscle, nerve and immune function.

• Bone health: Vitamin D helps maintain calcium and phosphate levels needed for normal bone mineralisation.

• Muscle function: Adequate vitamin D supports normal muscle function, although taking extra does not automatically improve strength.

• Immune function: Vitamin D is involved in normal immune activity, but supplements do not prevent every infection.

Understanding vitamin D deficiency

What is vitamin D deficiency?

Vitamin D deficiency means the body has too little vitamin D to support normal function. Severe or prolonged deficiency can impair bone mineralisation, causing rickets in children and osteomalacia in adults. It can also contribute to secondary hyperparathyroidism as the body tries to keep blood calcium stable. There is no single threshold that every organisation uses in every clinical situation. The National Institutes of Health Office of Dietary Supplements notes that the risk of deficiency rises when serum 25-hydroxyvitamin D is below 30 nmol/L, or 12 ng/mL, while levels of 50 nmol/L, or 20 ng/mL, or more are adequate for most people. Results should be interpreted by the treating clinician rather than against an online chart alone.

Symptoms of vitamin D deficiency

Many people have no clear symptoms. When deficiency is more severe or prolonged, possible signs include:

• Muscle weakness, particularly around the hips or thighs

• Diffuse bone pain or tenderness

• Difficulty rising from a low chair or climbing stairs

• A higher risk of falls or fractures in vulnerable adults

• Rickets in children or osteomalacia in adults

Fatigue, low mood and general aches are often discussed in relation to vitamin D, but they are non-specific. They should not be used to diagnose a deficiency without assessment.

Who is more likely to have low vitamin D?

• Limited sun exposure: Indoor work, covering most of the skin and spending little time outdoors can reduce vitamin D production.

• Darker skin: More melanin reduces the amount of vitamin D produced from the same ultraviolet exposure. Skin tone should be considered directly rather than using race as a biological shortcut.

• Older age: Ageing skin makes vitamin D less efficiently.

Malabsorption: Coeliac disease, Crohn’s disease, cystic fibrosis and some forms of bariatric surgery can reduce absorption.

• Liver or kidney disease: These organs are involved in converting vitamin D into forms the body can use.

• Some medicines: Certain anticonvulsants, glucocorticoids and other medicines can affect vitamin D metabolism.

Getting vitamin D from sunlight and food

Can you get enough vitamin D from sunlight?

Sunlight can contribute, but there is no safe universal number of minutes that works for everyone. Season, time of day, latitude, skin tone, clothing, age and sunscreen all change vitamin D production. Deliberate sunburn is not a vitamin D strategy. Follow local sun-safety advice and use food or supplements when a healthcare professional recommends them.

Foods that provide vitamin D

Few foods naturally contain much vitamin D. Useful sources include oily fish, egg yolk and fortified foods such as some milks, plant drinks and cereals. Food labels matter because fortification varies. Diet supports intake but may not be enough to correct a confirmed deficiency.

Testing and treatment

How is vitamin D deficiency diagnosed?

Doctors use a 25-hydroxyvitamin D blood test, often written as 25(OH)D, to assess vitamin D status. The 2024 Endocrine Society guideline does not recommend routine vitamin D testing for every healthy adult because the benefit of screening people without symptoms or established indications remains uncertain.

Testing may still be appropriate when a person has symptoms or conditions linked with bone disease, malabsorption, kidney or liver disease, or another recognised clinical reason. A healthcare professional should interpret the result alongside the wider medical picture.

How is vitamin D deficiency treated?

Treatment depends on how low the level is, why it became low and whether another condition is involved. A clinician may recommend a daily or short-term higher-dose vitamin D regimen, followed by maintenance intake. Vitamin D3 often raises 25-hydroxyvitamin D more effectively than vitamin D2, but the correct product and dose depend on the individual.

Do not copy a high-dose schedule from the internet. Vitamin D is fat-soluble, and excessive intake can cause hypercalcaemia, nausea, weakness, kidney stones and other serious problems. Follow-up testing may be needed after treatment, particularly when the deficiency was severe or absorption is impaired.

Support your daily nutrition

Aora Nutrivit Plus provides 19 essential nutrients and grape seed extract to complement daily nutrition. It is not a treatment for confirmed vitamin D deficiency and should not replace a vitamin D dose prescribed by a healthcare professional.

When should you see a doctor?

Arrange a medical assessment if you have persistent bone pain, marked muscle weakness, repeated fractures, difficulty walking or symptoms alongside a digestive, kidney or liver condition. Seek advice before using high-dose vitamin D, especially if you have kidney disease, high calcium levels, sarcoidosis or take regular medicines.

Related Reads

• Vitamin B12 Deficiency: Symptoms, Causes and Treatment

• Should You Take a Multivitamin? Benefits and Who May Need One

Medical Disclaimer: This article is for general educational purposes only and should not replace professional medical advice, diagnosis or treatment. Speak to a qualified healthcare professional if you have persistent bone pain, significant muscle weakness, repeated fractures or concerns about vitamin D deficiency. Do not use high-dose vitamin D without appropriate medical advice.